The concept of Digital Twin (DT) has emerged in recent years to facilitate the use of Building Information Modeling during the entire projects' lifecycle. In the DT concept, cyber-physical system theory is utilized to collect condition data about an existing asset and then integrate this data into the digital model. The major limitation though is that the current scope of DT is limited to the operation and maintenance phase. Nevertheless, the DT concept can be extended to the entire lifecycle of the asset if the relevant sensory and non-sensory data are incorporated into the digital model in an automated and systematic way. However, in the current literature, there is no clear insight about such a holistic and life-cycle DT concept for infrastructure projects. Especially, there is very little understanding about how various sensory and non-sensory data from construction and operation phases can be seamlessly integrated into the 3D BIM models. Therefore, this research aims to develop a conceptual model for the architecture of Lifecycle DT (LDT) focusing on bridges. To this end, an ontological modeling approach is adopted. The proposed ontology is validated through a workshop session where domain experts assessed the results with respect to some competency questions. The outcome of the session indicated that the proposed ontology scored sufficiently in all the criteria and succeeded in satisfying the information needs of the LDT. Overall, the proposed model offers an insight into a lifecycle modeling practice as well as automated data incorporation, enabling a smooth transition towards an upgraded modeling practice.